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High Temperature Tribology and

Jens Hardell Associate Professor Head of Division Division of Machine Elements Division of Machine Elements 15 senior researchers 20 PhD students Tribo-condition monitoring and control Modelling and simulation

Tribo-materials

Wear

Tribology Biotribology

Vehicles and machine Lubrication and components HT Research Resources and Infrastructure Reciprocating friction and Pin-on-disc up to 700 °C wear up to 900 °C

Nanoindentation up to 750 °C HT Research Resources and Infrastructure

Hot strip tribometer Test parameters Value Load 5000 N Temperature strip 1000 °C Temperature tool 700 °C velocity 250 mm/s Sliding distance 500 mm/strip

Tool pins Strip Background High temperature tribology – a complex process

FN Heat Adhesion v slide conduction

Abrasion Oxidation

Microstructural Diffusion changes

Thermal Thermal softening fatigue Tribology in hot stamping Quality N

vslide F

Fμ (T)=?

Wear behaviour?

Process economy Reduce Surface

Tribology in hot forming Surface quality of Friction control component

Minimise wear Aim and objectives Aims – Enhanced understanding of the effect of temperature on friction and wear processes – Efficient friction control and minimised wear at high temperatures Objectives – To experimentally characterise and understand the tribological behaviour of hot forming tool steels and ultra high strength boron steel both room and elevated temperatures – To investigate and understand the mechanisms governing friction and wear at different temperatures – To explore the potential of certain technologies Results – analysis of real tools

• Forming of Al-Si coated steel severely affected by galling – Tool surface altered by transferred material – Negative effect on formed components – Increased maintenance costs and downtime Results – analysis of real tools

Galling on actual Galling on pin forming tool specimen

Pin specimen Forming tool*

*Image from: http://help.solidworks.com/2013/English/SolidWorks/sldworks/HIDD_DVE_FORM_TOOL.htm Results – effect of contact pressure and on galling Results – effect of contact pressure and surface roughness on galling Results – effect of contact pressure and surface roughness on galling 10 MPa

60 50 40 30 20 10 Covered areaCovered (%) Perpendicular sliding Parallel sliding 0 Perpendicular to Parallel to surface lay surface lay • Sliding parallel to surface lay significantly reduces galling • Debris pushed out of the contact – Observed accumulation of debris at the edge Future research needs

• Tribological performance of “new” workpiece materials and sheet coatings

• Development and characterization of surface engineering for hot forming tools

• High temperature lubrication – understanding mechanisms and formulating customized products